Organic compositions containing antioxidants



3,493,511 ORGANIC COMPOSITIONS CONTAINING ANTIOXIDANTS Derek A. Law, Pitman, N.J., assignor to Mobil Oil Corporation, a corporation of New York No Drawing. Filed Dec. 28, 1966, Ser. No. 605,185 Int. Cl. C10m /20, 3/28, 1/34 U.S. Cl. 25251.5 Claims ABSTRACT OF THE DISCLOSURE Improved antioxidant properties are provided organic base media, such as lubricating oils, by the presence of monoaminoor diamino(aromatic) quinones admixed with an aromatic compound, such as diarylamines, arylazoaromatic compounds, and hindered phenols.

This invention relates to additives for organic compositions and particularly to lubricating oil compositions having improved oxidation stability.

Many industrial organic media are used under circumstances which contribute to their breakdown during service by oxidation. Such media include lubricants and greases, hydraulic fluids for brake and transmission systems, resins and plastics for coatings and structural articles. The severe operating conditions of modern engines, for example, including automotive and gas turbine engines, have often caused lubricating oils to deteriorate rapidly during use. This excessive rate of oxidation is accelerated by the use of higher engine operating temperature than formerly used. Oxidative deterioration of the oil is usually accompanied by the formation of gummy deposits, sludge, acids which may be strong enough to cause metal corrosion, and other products of chemical breakdown. These products may seriously interfere with the lubrication operation.

Organic media are generally blended with additives termed antioxidants which protect against the effects of oxidation. Although many of the older known additives have been found to be adequate in stabilizing some modern mineral oil lubricant and synthetic lubricant blends the discovery of new and more effective additives would be highly desirable.

It is a major object of this invention to provide novel organic compositions which have improved oxidation stability. Another object is to provide improved lubricating oil compositions capable of withstanding the oxidizing conditions of modern engines. These and other objects will become apparent from the following disclosure.

It has now been discovered that organic compositions ordinarily susceptible to deterioration caused by oxidation may have improved resistance by the addition thereto of a minor amount of a synergistic mixture of an aminoquinone with an aromatic amine or hydroxy co-additive compound. Preferably this co-additive compound contains at least two aromatic rings, and includes (1) diarylamines, (2) an arylazophenol or arylazonaphthol, or arylazoarylamine or arylazodiarylamine or (3) a hindered phenol, although single ring compounds, such as phenol, phenyl amine and alkyl-phenyl amine may be employed. The mixtures of this invention surprisingly afford a higher degree of stabilization in the presence of oxygen under catalytic conditions than either of the additives alone, at the same concentrations as the mixtures,

The aminoquinones used in this invention have the general structure wherein Q is benzoquinone, naphthoquinone or substituted derivatives thereof and R and R may each be hydrogen, hydrocarbyl or substituted hydrocarbyl. At least one of ice R and R is always a hydrocarbyl or substituted hydrocarbyl group. The term hydrocarbyl for the purpose of this invention, includes such organic groups as alkyl, alkenyl, cycloalkyl, aralkyl and substituted derivatives thereof, including groups containing oxygen, sulfur, nitrogen and halogen atoms, such as alkylaminoalkyl, haloalkyl, hydroxyalkyl, alkoxyalkyl, acyloxy and haloalkyl; or aryl, alkaryl and substituted derivatives thereof containing oxygen, sulfur, nitrogen and halogen groups; and n is 1 to 2. Each R or R group may be the same as another or several other R or R groups, or dilfcrent therefrom. Also, the two groups attached to each nitrogen atom may be bonded in a cyclic structure to produce heterocyclic amino groups attached to the nucleus of the quinone. Thus R and R groups may be part of aziridyl, azetidyl, pyrrolidyl, tetrahydroquinolyl, and piperidyl radicals. The number of aliphatic carbon atoms for the organo groups either individually or as representing a heterocyclic radical may range from 1 to about 40 carbon atoms.

The aminoquinones of this invention preferably have the following specific structures 0 II H N\ R N\ Y l I i R (IL RI RI/ I] N l wherein the R and R groups have the above-mentioned definitions, and R" has the same definition as R and R and may be also halogen, hydroxy, alkoxy acyloxy, acylamines, carboalkoxyl or substituted derivatives of these. The preferred substituents are those organo or substituted organo groups, and especially alkyl or substituted alkyl, having from 1 to about 20 carbon atoms.

Although the alkyl groups on each nitrogen atom may be different, symmetrical alkyl amines are employed herein to illustrate the essential features of this invention.

The aminoquinones used in this invention may be prepared by the reaction between a quinone and a primary or secondary amine. In the latter reaction, the reactants are dissolved in a suitable solvent and a stream of air or oxygen or other oxygen-containing gas is dispersed therethrough with agitation at room temperature. Alternatively, the oxidation step may be performed with an oxidizing agent, such as hydrogen peroxide, potassium permanganate, manganese dioxide, potassium ferricyanide, and the like. The mole ratio of the reactants may be varied to produce the desired product. Approximately a 0.5 :1 to 1:1 ratio of amine to quinone may usually be used to produce monoaminobenzoquinones and naphthoquinones; a 2:1 to 10:1 ratio for the diarninobenzoquinone. It is preferred to have an excess of amine present in the reaction mixture.

As indicated above, the amine reactant may be a simple alkyl or cycloal'kyl amine, having from 1 to about 40 carbon atoms. Representative of these amines are ethylamine, butylamine, t-butylamine, t-octylamine, t-eicosylamine, n-hexylamine, n-octylamine, n-dodecylamine, n octadecylamine and cyclo-hexylamine. The substituted hydrocarbyl amines include hydroxyethylamine, 1,1-dimethyl-2-hydroxyethylamine, bis(hydroxymethyl)methylamine, ethylenediamine, di-ethylaminoethylamine, and diethylaminopropylamine. Secondary and heterocyclic wherein Ar and Ar may each be phenyl, naphthyl, and substituted phenyl and naphthyl, including alkyl substituents, having from 1 to 20* alkyl carbon atoms, and halogen substituents. Such compounds as diphenylamine, dinaphthylamine, N-phenyl-l-naphthylamine, and N-phenyl-2-naphthylamine are suitable in this invention. Their preparation is well known commercially and does not constitute a part of this invention.

The second co-additive is an arylazoaryl compound, similar to those disclosed and claimed in a copending application, Ser. No. 528,351, filed on Feb. 18, 1966, now US. No. 3,378,491. Suitable compounds are those of the structure wherein L is a hydroxy or amine radical. The aromatic rings are phenyl or naphthyl. The aromatic nuclei Ar and Ar may be substituted in the manner deescribed in the said copending application by the Y and Y groups consisting of alkyl, alkaryl, aryl, aralkyl, alkoxy or aryloxy having from 1 to about 20 carbon atoms in each group, or amino, organo-substituted amino, or an additional organo-azo group. Of particular interest is l-phenylazo-N-phenyI-Z-naphthylamine.

The third group of co-additives includes the hindered phenols. These phenols are typically the hydroxyaryl compounds of the general structures wherein X may be an alkylene group having from 1 to carbon atoms, such as methylene or 2,2-propylene, oxygen or sulfur, and y and z may each be 1 or 2. Ar and Ar may be each phenyl, naphthyl, or anthracenyl and have Y and Y substituents attached in positions adjacent to the hydroxy group, such as alkyl, aryl or non-hydrocarbyl substituents. These hindered phenols, or bisphenols are also prepared by methods well known in the art. Preferred substituents are alkyl radicals of from 1 to carbon atoms, occupying from 1 to 4 available positions on the nucleus. Tertiary alkyl-substituted compounds, such as bis-di-t-butylphenols are most preferred.

We have found that, in accordance with this invention, the presence of these mixtures of the aminoquinones and the coagents prevent the breakdown of industrial organic substances normally susceptible to oxidation deterioration when subjected to oxidation and other deteriorative forces, particularly at high temperatures. These synergistic mixtures have been found to reduce the formation of acids and the viscosity change in lubricating compositions during use in an unexpectedly improved manner. Such organic substances as plastics and rubbers, including polyurethanes, polyvinyls, conjugated diene polymers, and copolymers (such as GR-S rubbers), silicone rubbers, and the like may be used in this invention.

The organic substances of primary interest in this invention are lubricating oil composition heat-transfer fluids or power transmission fluids, in which the base medium is a hydrocarbon mineral oil or one of the synthetic lubricating fluids, the latter being suitable for use in gas turbine engines, such as jet aircraft engines. Such synthetic fluids include polyolefin fluids, polyalkylene oxide fluids, silicone polymer fluids, polyarylether fluids, polyacetals, and organic ester fluids. This latter class includes diesters, such as those prepared from dicarboxylic acids and monohydric alcohols or glycols and monocarboxylic acids, triesters including, for example, esters prepared from dimethylpropane and monocarboxylic acids, and tetraesters prepared from pentaerythritol and monocarboxylic acids, the acids in these ester fluids having from about 1 to about 30 carbon atoms. Special attention is given in this invention to the tetraester fluids of pentaerythritol and monocarboxylic acids. Solid lubricants, such as greases, are also benefited by the additive combinations of this invention.

The following illustrative examples are intended to describe the invention more fully and are not deemed a limitation of the scope thereof. All parts and percentages are by weight unless otherwise specified.

Example 1: Preparation of 2,5-bis-n-butylaminobenzoquinone.In a suitable reactor 165 grams (1.5 moles) of hydroquinone was dissolved in 1 liter of methanol, and 230 grams (3.15 moles) of n-butylamine was added at 25 C. As the mixture was stirred, the temperature rose to 40 C. during which a color change was observed. After 5 minutes of stirring, a slow stream of oxygen was passed through the mixture. The temperature rose to 51 C. over a 2-hour period. A red crystalline product commenced to precipitate. The total oxygen treatment lasted for 16 hours. Afterward, the solid was filtered oif and washed in methanol, yielding 237 grams (63%) of product; M.P. 157 158 C.

Analysis.-Calcd: C, 67.31%; H, 8.87%; N, 11.19%. Found: C, 67.34%; H, 8.48%; N, 11.30%.

Example 2: Preparation of 2,5-bis-n-octylaminobenzoquinone.Following the method of Example 1, n-octylamine was reacted with hydroquinone. The oxidation was carried out for a period of 24 hours. A yield of 63% of crude product, M.P. 134 C., was obtained.

Analysis.Calcd: C, 72.87%; H, 10.56%; N, 7.73%. Found: C, 73.08%; H, 10.35%; N, 7.71%.

Example 3: Preparation of 2,5 bis cyclohexylaminobenzoquinone.-Following the method of Example 1, cyclohexylamine was reacted with hydroquinone. The oxidation was carried out for a period of 19 hours. A yield of 34% of crude product, M.P. 208 C., was obtained.

Analysis.-Calcd: C, 71.48%; H, 8.67%; N, 9.25%. Found: C, 71.18%; H, 8.04%; N, 9.66%.

The co-additives in the mixtures tested in the illustrative examples are prepared by known methods, as indicated heretofore. With respect to the l-phenylazo-N-phenyl- Z-naphthylamine, the preparation is as follows:

In a suitable reactor was added 31 parts of aniline dissolved in 160 parts of 50% hydrochloric acid. To this solution was added dropwise 23 parts of sodium nitrite in parts of water. The temperature of the reaction mixture was maintained in the range of 0 to 3 C. The resulting solution of benzene diazonium chloride held at a temperature of 0 was added to a suspension of 55 parts of N-phenyl-2-naphthylamine and parts of sodium acetate in 1000 parts of ethanol.

The reaction mixture was warmed to reflux and then cooled to room temperature and the product filtered off. The product was washed with cold water and cold ethanol and finally air dried leaving 69.9 grams (87% theory) of a scarlet powder; M.P. 123128 C. This powder was recrystallized from acetone, the crystals having an M.P. of 143 to 144 C. The total yield was 93% to 96%.

Analysis.-Calcd: C, 81.71%; H, 5.29%; N, 12.99. Found: C, 80.96%; H, 5.34%; N, 12.50%.

EVALUATION OF PRODUCTS (a) 15.6 sq. in. of sand-blasted iron wire,

(b) 0.78 sq. in. of polished copper wire,

(c) 0.87 sq. in. of polished aluminum wire, and (d) 0.167 sq. in. of polished lead surface.

Inhibitors for oil are rated on the basis of prevention of oil deterioration by measuring the increase in acid formation or neutralization number (NN) and kinematic viscosity (KV) occasioned by the oxidation. The results of the tests are reported in the tables below.

These results indicate that the synergistic mixtures of this invention posses improved antioxidant properties in comprison with known commercial antioxidants. Such results are unexpected since the naphthylamine and bisphenol antioxidants have achieved such wide acceptance in the lubricating industry for synthetic fluids and represent a criterion for the development of new antioxidants. These mixtures may be used not only in the present base esters, as indicated in the above test but also in hydrocarbon oils, and other synthetic oils, such as in the triesters and diesters, as well as in other oxidation-prone organic compositions. Moreover, the fluid compositions may contain other additives such as detergents, other antioxidants, pour point depressants, extreme pressure agents and the like.

Although this invention has been described with the aid of specific illustrations and working examples, the scope of this invention is not limited except as indicated in the following claims.

I claim:

1. An organic composition comprising a major proportion of an organic compound normally susceptible to oxidative deterioration and a minor proportion in amounts suflicient to decrease such deterioration of a synergistic mixture of TABLE A Concen- Percent trationt, NN inegeltsxe w 0 Inhibitor percent increase at 100 F.

None 7. 9 265 2,5-bis-n-butylaminobenzoquinone. 0. 5 0. 46 4 N-Phenyl-l-naphthylamine l. 0 0. 8 15 2,5-bis-n-butylaminobenzoquinone. .25 0 32 3 N-Phenyl l-uaphthylamine 1111 2,5-bis-n-butylaminobeuzoquinon 0.125 0 46 3 N-Phenyl-l-naphthylamine. 0. 375 N-PhenyI-Z-naphthylamine l. 0 0. 43 6 2,5-bis-n-butylaminobenzoqui .25 0 07 4 N-Phenyl-Z-naphthylamine 75 2,fi-bis-n-butylaminobenzoqul 0.125 0 12 3 N-Phenyl-Z-naphthylamine 0. 375 l-phenylazo-N-phenyl 2napl1th 2. 0 0. 6 8 2,5-bis-n-butylaminobenzoquinone. 0. 5 0 7 3 1-phenylazo-N-phenyl Z-naphthylami 1. 5 3,5,3 ,5-tetra t-butyl, 4,4-dihydr0xydiphe 0.5 1 5. 1 1 200 2,fi-bis-n-butylaminobenzoquinone 0.125 1 3 6 1 75 3,5,3,5-tet1'a-t-butyl,4,4-dihydroxydiphenylmethane 0. 375 3.5,35-tetra-t-butyl,4,4-dihydroxydiphenyl 0. 5 7. 1 148 2,5-bis-n-butylaininobenzoquinone 0. 125 0 5 3 3,5,3,5-tetra-t-butyl 4,4-dihydroxydiphenyl 0. 375

TABLE B Concen- Percent tratiork, NN incgelase w o Inhibitor percent increase at F.

None 7.9 265 2,5bis-n-octylaminobenzoquinone 0. 5 0. 75 8 2,5-bis-n-oetylaminobenzoquinone 0.25 0 08 N-phenyl-2-naphthylamine 0. 75 2,5bis-n-oetylaminobenzoquinone- 0.125 1 0 12 3 N-pl1enyl-2-naphthylamine 0.375 1 3,5,3,5-tetra-t-butyl 4,4-dihydroxydiphenyl 1.0 6. 0 96 2,5bis-n-octylamin0benzoquinone 0.25 I; 0 62 3,5,3,5tetra t-butyl 4,4-dihyd roxydiphenyl 0. 75 2,5bis-n-octylaminobenzoquinone 0. 0 62 4 3,5,3 ,5-tetra-t-butyl 4,4-dihydroxydiphenyl 0. 375

TABLE 0 (1) an aminoquinone having the structure Percent I Ctongenincrease R n ra 1011 o Inhibitor i at 70 wherein Q is selected from the group consisting of benzoquinone, naphthoquinone, and the hydrocarbyl None 2,5-bis-cyclohexylaminobenzoquino 2,5-bis-cyclohexylaminobenzoquinon 0.25 O 22 2 N-pheny1-2-naphthylamine. 0. 75 2,5biseyclol'lexylarninobenzo 0.125 0 12 3 N -phenyl-2naphthylamine O. 37 5 7 5 substituted derivatives thereof, the said hydrocarbyl having from about 1 to about 40 carbon atoms, R and R are individually selected from the group consisting of hydrogen, alkyl, and cycloalkyl, and wherein R and R may be members of the same heterocyclic amino radical each attached to the nitrogen atom, wherein at least one of R and R is an organic radical, said radical containing from 1 to about 40 carbon atoms, and n is an integer of 1 to 2, and (2) an aromatic compound selected from the group consisting of (a) a diarylamine having the structure I F [A1 NH Ar wherein Ar and Ar are each selected from the group consisting of phenyl, naphthyl, alkylphenyl, and alkylnapthyl, and (b) a phenol having the structure selected from the group consisting of HO Ar Ar OH, and HO- Ar X Ar OH L13 LaJ Lei LaJ wherein Ar and Ar are each selected from the group consisting of phenyl and napthyl, X is alkylene having from 1 to 5 carbon atoms, and Y and Y are each selected from the group consisting of alkyl and aryl radicals, the alkyl radical having from 1 to 20 carbon atoms.

2. The composition of claim 1 wherein the organic compound is a lubricating oil.

3. The composition of claim 2 wherein the lubricating oil is a synthetic fluid lubricant.

4. The composition of claim 3 wherein the synthetic fluid lubricant is an ester of a pentaerythritol and a monocarboxylic acid having from 1 to about 30 carbon atoms.

5. The composition of claim 1 wherein the diarylamine is a phenylnaphthylamine.

6. The composition of claim 1 wherein the hindered phenol is 3,5,3',5-tetra-t-butyl 4,4'-dihydroxydiphenyl.

7. The composition of claim 1 wherein the quinone is 2,5-bis-n-buty1amino-benzoquinone.

8. The composition of claim 1 wherein the quinone 1s 2,S-bis-n-octylaminobenzoquinone.

9. The composition of claim 1 wherein the quinone is 2,5-bis-cyclohexylaminobenzoquinone.

10. The composition of claim 1 wherein the aminoquinone is a 2,5-bis-organoaminobenzoquinone having the structure II R N ll wherein R and R' are individually selected from the group consisting of hydrogen and alkyl having from 1 to 20 carbon atoms.

References Cited FOREIGN PATENTS 952,151 3/1964 England.

DANIEL E. WYMAN, Primary Examiner r W. J. SHINE, Assistant Examiner U.S. Cl. X.R. 252-401, 404 

